Intra prediction method and apparatus, and image encoding/decoding method and apparatus using same

ABSTRACT

A video decoding apparatus using an intra prediction, includes: a decoder to decode a bitstream to thereby extract residual signals; an inverse quantizer to inversely quantize the residual signals; an inverse transformer to inversely transform the inversely quantized residual signals; an intra predictor to predict a current block from a plurality of neighboring blocks of the current block; and an adder to add the inversely transformed residual signals to the predicted pixels in the predicted block, wherein the intra predictor includes a weighted pixel calculator to calculate a plurality of weighted pixel values of pixels selected in the neighboring blocks by applying weights to the pixels selected in the neighboring blocks, the weights being decided variably based on a position of a current pixel to be predicted in the current block; and a pixel predictor to derive a predicted pixel value of the current pixel using the weighted pixel values.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. patent applicationSer. No. 13/947,403 filed Jul. 22, 2013, which is a continuation of U.S.patent application Ser. No. 13/001,611 filed Mar. 18, 2011, which is athe National Phase application of International Application No.PCT/KR2009/003237, filed Jun. 17, 2009, which is based upon and claimsthe benefit of priority from Korean Patent Application No.10-2008-0059322, filed on Jun. 24, 2008. The disclosures of theabove-listed applications are hereby incorporated by reference herein intheir entirety.

TECHNICAL FIELD

The present disclosure relates to a method and apparatus for determiningan intra prediction mode, and a method and apparatus forencoding/decoding video using the same. More particularly, the presentdisclosure relates to an intra prediction method and apparatus forcarrying out prediction encoding and decoding of a current block of animage from its neighboring block in a way to minimize the differencebetween the original current block and a predicted current block, and toan image encoding/decoding method and apparatus using the same.

BACKGROUND ART

The statements in this section merely provide background informationrelated to the present disclosure and do not constitute prior art.

Moving Picture Experts Group (MPEG) and Video Coding Experts Group(VCEG) have developed an improved and excellent video compressiontechnology over prior MPEG-4 Part 2 and H.263 standards. The newstandard is called H.264/AVC (Advanced Video Coding) and was releasedsimultaneously as MPEG-4 Part 10 AVC and ITU-T Recommendation H.264.H.264/AVC (shortened as H.264 hereinafter) differently uses a spatialpredictive coding method relative to existing video coding-relatedinternational standards of MPEG-1, MPEG-2, MPEG-4 Part2 Visual, etc.

Known methods use “intra prediction” for coefficients transformed inDiscrete Cosine Transform Domain (or DCT Transform Domain) to seekhigher encoding efficiency resulting in degradation of the subjectivevideo quality at low band transmission bit rates. In contrast, H.264adopts the method of encoding based on a spatial intra prediction in aspatial domain rather than in a transform domain.

Encoders using an encoding method based on the known spatial intrapredictions take information on the previously encoded and reconstructedblock to predict current block information therefrom, encode informationon just the difference of the predicted block from the original block tobe encoded, and transmit the encoded information to a decoder. At thistime, the encoder may transmit parameters needed for prediction of theblock information to the decoder, or the encoder and decoder may besynchronized so that they share the needed parameters for the decoder topredict the block information. On the other hand, the desired block tobe currently decoded is generated and reconstructed by first predictingits neighboring blocks that are completely decoded and reconstructed andthen obtaining the sum of difference information or residual datatransmitted from the encoder and the predicted neighboring blockinformation. Then, also, if the parameters needed for the prediction aretransmitted from the encoder, the decoder uses the same to predict theneighboring block information.

There are different intra predictions such as an intra_(—)4×4prediction, intra_(—)16×16 prediction, and intra_(—)8×8 prediction amongothers, where the respective intra predictions include a plurality ofprediction modes.

FIG. 1 is an exemplary diagram showing conventional nine 4×4 intraprediction modes.

Referring to FIG. 1, the intra_(—)4×4 prediction has nine predictionmodes which include a vertical mode, horizontal mode, direct current(DC) mode, diagonal down-left mode, diagonal down-right mode,vertical-right mode, horizontal-down mode, vertical-left mode andhorizontal-up mode.

FIG. 2 is an exemplary diagram showing known four 16×16 intra predictionmodes.

Referring to FIG. 2, the intra_(—)16×16 prediction has four predictionmodes which include a vertical mode, horizontal mode, DC mode and planemode. The intra_(—)8×8 prediction also has four modes similar to theintra_(—)16×16 prediction.

In an intra prediction that uses the DC mode as the prediction mode (orin a ‘DC mode prediction’ in short), the result is an average valueobtained in a unit of block. Here, the average value means an average of8 pixels (for the case of intra_(—)4×4 prediction) from the currentblock's left side 4 pixels plus the current block's upper side 4 pixelsor an average of 32 pixels (for the case of intra_(—)16×16 prediction)from the current block's left side 16 pixels plus the current block'supper side 16 pixels. Therefore, in performing the DC mode prediction,the neighboring blocks to the current block are averaged for predictingall of the 4×4 pixels or the 16×16 pixels.

Hence, regardless of the type of prediction which is intra_(—)4×4prediction or intra_(—)16×16 prediction or another, the predictionvalues or predictors are the same with respect to the current block's 16pixels for the case of intra_(—)4×4 prediction or 256 pixels for thecase of intra_(—)16×16 prediction. The inventor(s) has experienced thatthis lowers the accuracy of predicting the current block to cause adecrease of coding efficiency or compression efficiency.

In addition, the inventor(s) has experienced that the dropped predictionaccuracy will increase the differential value between the original blockand the predicted block whereby the above DC mode prediction produces agreater amount of the difference information and a decline in the videocompression efficiency disadvantageously.

SUMMARY

In accordance with some embodiments of the present disclosure, a videodecoding apparatus using an intra prediction comprises a decoder, aninverse quantizer, an inverse transformer, an intra predictor and anadder. The decoder is configured to decode a bitstream to therebyextract residual signals. The inverse quantizer is configured toinversely quantize the residual signals. The inverse transformer isconfigured to inversely transform the inversely quantized residualsignals. The intra predictor is configured to predict a current blockfrom a plurality of neighboring blocks of the current block. The adderis configured to add the inversely transformed residual signals to thepredicted pixels in the predicted block. The intra predictor comprises aweighted pixel calculator configured to calculate a plurality ofweighted pixel values of pixels selected in the neighboring blocks byapplying weights to the pixels selected in the neighboring blocks,wherein the weights are decided variably based on a position of acurrent pixel to be predicted in the current block; and a pixelpredictor configured to derive a predicted pixel value of the currentpixel using the weighted pixel values. The pixels selected in theneighboring blocks comprise: a first pixel which is included in an upperneighboring block and located at the same column with the current pixel;and a second pixel which is included in a left neighboring block andlocated at the same row with the current pixel.

DESCRIPTION OF DRAWINGS

FIG. 1 is an exemplary diagram showing known nine 4×4 intra predictionmodes,

FIG. 2 is an exemplary diagram showing known four 16×16 intra predictionmodes,

FIG. 3 is a block diagram of an electronic configuration of a videoencoding apparatus according to an aspect,

FIG. 4 is a block diagram of an electronic configuration of an intraprediction apparatus according to an aspect,

FIG. 5 is a flow diagram of an intra prediction method according to anaspect,

FIG. 6 is a flow diagram of a process of calculating weighted pixelvalues of adjacent pixels to respective pixels in a current blockaccording to an aspect,

FIG. 7 is a flow diagram of a video encoding method according to anaspect,

FIG. 8 is a block diagram of an electronic configuration of a videodecoding apparatus according to an aspect,

FIG. 9 is a flow diagram of a video decoding method according to anaspect, and

FIG. 10 is an exemplary diagram a process of predicting the currentblock by using a weighted value by pixel distances according to anaspect.

DETAILED DESCRIPTION

Hereinafter, aspects of the present disclosure will be described indetail with reference to the accompanying drawings. In the followingdescription, the same elements will be designated by the same referencenumerals although they are shown in different drawings. Further, in thefollowing description of the present disclosure, a detailed descriptionof known functions and configurations incorporated herein will beomitted when it may make the subject matter of the present disclosurerather unclear.

Some embodiments of the present disclosure are provided to principallyimprove the video compression efficiency by closing the gap between theoriginal block and the predicted block in performing the intrapredictions for predicting the current video block.

FIG. 3 is a block diagram of an electronic configuration of a videoencoding apparatus 300 according to an aspect of the present disclosure.

Video encoding apparatus 300 of this aspect is adapted to predict avideo current block using one or more of its neighboring blocks in orderto encode the video, and may include an intra predictor 310, asubtractor 320, a transformer 330, a quantizer 340, and an encoder 350.

Video encoding apparatus 300 may be a personal computer or PC, notebookor laptop computer, personal digital assistant or PDA, portablemultimedia player or PMP, PlayStation Portable or PSP, or mobilecommunication terminal, smart phone or such devices, and represent avariety of apparatuses equipped with, for example, a communicationsystem such as a modem for carrying out communications between variousdevices or wired/wireless communication networks, a memory for storingvarious programs for encoding videos and related data, and amicroprocessor for executing the programs to effect operations andcontrols.

Intra predictor 310 predicts in a video the current block by using itsneighboring block, and specifically by calculating predicted pixelvalues of respective pixels in the current block with a weight valueapplied to one of more pixel values of one or more of the neighboringblocks. Here, the neighboring block may mean one or more blocks whichare compressed prior to and positioned adjacent to the current block,and specifically one or more of left side blocks of the current blockand upper side blocks of the current block.

In addition, intra predictor 310 may exclusively have a DC mode intraprediction perform the intra prediction process on the current blockwith the weight value applied, wherein the DC mode is to predict anaverage of the pixel values of the one or more adjacent pixels in theneighboring block to the current block for the pixel values of thecurrent block. In addition, the weight value may be variably applieddepending on the distances between respective pixels in the currentblock and the respective one or more adjacent pixels in the one or moreneighboring blocks.

When using the DC intra prediction mode which had typically predictedthe respective current block pixels by averaging the pixel values of theone or more relatively adjacent pixels in the neighboring block to thecurrent block, intra predictor 310 does not simply jump from averagingthe adjacent pixels' values to predicting the averaged value as thepixel values of the entire current bock pixels but does calculations ofweighted pixel values by variably setting and applying weights to thepixel values of the adjacent pixels depending on the distances betweenthe respective current block pixels and their adjacent pixels and thenaverages these weighted pixels values so as to make a prediction for thepixel values of the entire current block pixels. The “adjacent pixels”herein may refer to the pixels within the blocks that are neighboringthe current block although they may be within the neighboring blocks andnot close to the current block. Intra predictor 310 will be describedbelow in more detail referring to FIG. 4.

Subtractor 320 generates a residual signal from the difference betweenthe original pixel value of each pixel in the current block and apredicted pixel value of each pixel in the current block.

Transformer 330 transforms the residual signal generated from subtractor320 into a frequency domain. Here, transformer 330 may perform thefrequency domain transform through various transforming techniques ofvideo signals from on a temporal axis onto a frequency axis such asdiscrete cosine transform (called DCT) or wavelet transform.

Quantizer 340 performs a quantization with respect to the transformedfrequency domain residual signal from transformer 330. Encoder 350encodes the quantized residual signal from quantizer 340 into abitstream. Although various other coding techniques are unrestricted foruse in the disclosure, entropy coding may be adopted herein.

FIG. 4 is a block diagram of an electronic configuration of an intraprediction apparatus according to an aspect.

The intra prediction apparatus may be implemented by intra predictor 310when it is applied to video encoding apparatus 300 described withreference to FIG. 3. Hereinafter, the intra prediction apparatus will beconveniently and simply called intra predictor 310.

Intra predictor 310 in this aspect predicts in a video the current blockby using one or more of its neighboring blocks, and specifically itcarries out predictions with respect to pixel values of respectivepixels in a current block by performing weighted averaging of pixelvalues of one or more adjacent pixels in the one or more neighboringblocks depending on the distances between the respective pixels in thecurrent block and the respective one or more adjacent pixels.

Intra predictor 310 may comprise a weighted pixel value calculator 410and a predicted pixel value calculator 420, and it is adapted to predictthe current block by calculating predicted pixel values of therespective pixels in the current block through applying a weight valueto one or more pixel values of the one or more neighboring blocks.

Weighted pixel value calculator 410 applies the weight value to thepixel value(s) of each of the adjacent pixel(s) in the neighboringblock(s) to the current block to be encoded so as to calculate theweighted pixel values of the adjacent pixel(s).

Here, weighted pixel value calculator 410 may differently perform theweighting operation depending on calculations of the distances betweenthe positions of the respective pixels in the current block and those oftheir respectively adjacent pixels, and may calculate the weighted pixelvalues of the adjacent pixels according to the variable weightapplications depending on the pixel-to-pixel distances. Additionally, inthe weighting operation on the adjacent pixel values, weighted pixelvalue calculator 410 may apply the weight value in inverse proportion tothe calculated distances.

Specifically, weighted pixel value calculator 410 may apply a largerweight value to the neighboring block pixel value in response to acloser distance between the current block pixel and its neighboringblock pixel that implies the pixels' strong resemblance, whilecalculator 410 may apply a smaller weight value to the neighboring blockpixel value in response to a farther distance between the current blockpixel and its neighboring block pixel that implies the pixels' weakresemblance. In this way of weighting in inverse proportion to thedistances between the current block pixels and their neighboring blockpixels, it becomes possible to further reduce the disparity between thecurrent block and the prediction block with the pixel-to-pixelsimilarities considered in the intra prediction that performs in the DCprediction mode (hereinafter called ‘DC mode prediction’ in short).

Predicted pixel value calculator 420 calculates the predicted pixelvalues of the respective pixels in the current block using the weightedpixel values calculated for the adjacent pixel(s) by weighted pixelvalue calculator 410. Further, predicted pixel value calculator 420 maycalculate the predicted pixel values of the respective pixels in thecurrent block by averaging the weighted pixel values of the adjacentpixel(s) with respect to the respective pixels in the current block.

FIG. 5 is a flow diagram of an intra prediction method according to anaspect.

In the video encoding operation, video encoding apparatus 300 improvesthe encoding efficiency by reducing the encoded data amount throughencoding the difference between the original pixel value of the currentblock to be encoded and the predicted pixel value of the current blockthat is predicted, the pixel difference being a residual signal.

For this purpose, intra predictor 310 predicts the video current blockby using its neighboring block(s) as described above, and calculatesweighted pixel values of adjacent pixels with respect to respectivepixels in the current block that is the subject to encode in step S510.In other words, intra predictor 310 calculates the weighted pixel valuesof the one or more adjacent pixels by applying a weight value to therespective adjacent pixel(s) included in the neighboring block(s) (andbeing adjacent to the current block in particular).

In addition, when the weighted pixel values of the adjacent pixels arecalculated, intra predictor 310 calculates predicted pixel values of therespective pixels in the current block by using those weighted adjacentpixel values in step S520. Here, intra predictor 310 may calculate thecurrent block's respective predicted pixel values by averaging the oneor more adjacent blocks' weighted pixel values.

Intra predictor 310, in step S510 of calculating the weighted pixelvalues of the adjacent pixels with respect to the respective currentblock pixels, may count the distances between the positions of therespective current block pixels and the adjacent pixels to differentlyperform the weighting operation.

FIG. 6 is a flow diagram of a process of calculating weighted pixelvalues of adjacent pixels to respective pixels in a current blockaccording to an aspect.

Upon deciding the subject block to be encoded in a video that is thecurrent block, intra predictor 310 selects from its neighboring blocksof the video one or more adjacent pixels with respect to the currentblock in step S610. Here, the selected adjacent pixels may be one ormore of all the adjacent pixels in a left side block of the currentblock, or one or more of all the adjacent pixels in an upper side blockof the current block, or the entire adjacent pixels of the left andupper side blocks, although they are not so restricted but include allof the pixels in the current block's surrounding blocks (with right sideand lower side blocks).

With the adjacent pixel(s) selected, intra predictor 310 calculates thedistances between the positions of the respective current block pixelsand the positions of the respective adjacent pixels in step S620. Uponcalculating such pixel-to-pixel distances, intra predictor 310differently set the weight value depending on the calculated distancesin step S620 for applying the set weight value to the pixel values ofthe adjacent pixel(s) to calculate weighted values of the adjacentpixel(s) in step S630.

Specifically, when the neighboring block adjacent pixels are selected asin step S610, intra predictor 310 chooses a particular one of the entirecurrent block pixels to calculate its distances to the respectiveselected adjacent pixels. In differently setting the weight valuedepending on the respective adjacent pixels' calculated distances fromthe particular pixel and variably weighting the respective adjacentpixel values, intra predictor 310 responds to a longer pixel distancefor applying a smaller weight value and to a shorter pixel distance forapplying a larger weight value, thereby counting the similarity betweenthe particular pixel and adjacent pixels. In this way, the calculationof weighted adjacent pixel values is performed with the variableweighting according to the different pixel distances. Intra predictor310 repeatedly performs the calculation of the weighted adjacent pixelvalue with respect to the particular current block pixel for all of thepixels.

Upon completing the calculation of weighted pixel values throughdifferently weighting the adjacent pixel values by the distances of theadjacent pixels to the entire current block pixels, intra predictor 310calculates a predicted pixel value for a particular pixel of the currentblock by averaging the weighted adjacent pixel values for the particularpixel which is repeatedly performed for the entire pixels of the currentblock to calculate predicted pixel values for the entire current blockpixels.

FIG. 7 is a flow diagram of a video encoding method according to anaspect.

Video encoding apparatus 300 according to an aspect described withreference to FIG. 3 uses the intra predicting apparatus of intrapredictor 310 in the intra prediction method described with reference toFIGS. 4-6 in predicting the video current block to encode the video.

Specifically, video encoding apparatus 300 predicts the current block bycalculating the predicted pixel values of respective current pixels byapplying a weight value to the adjacent pixel value(s) in step S710,generates residual signals by calculating the differences between theoriginal pixel values of the respective current block pixels and thepredicted pixel values of the respective current block pixels in stepS720, transforms the residual signals into the frequency domaintransform through various transforming techniques such as DCT or wavelettransform in step S730, and quantizes the frequency domain-transformedresidual signals in step S740, and encodes the quantized residualsignals into a bitstream in step S750.

As described above, the encoded bitstream of video by the video encodingapparatus 300 may then be transmitted in real time or non-real-time tovideo decoding apparatuses for decoding the same into thereconstructions and reproductions via a wired/wireless communicationnetwork including the Internet, a short range wireless communicationnetwork, a wireless LAN network, WiBro (Wireless Broadband) also knownas WiMax network, and mobile communication network or a communicationinterface such as cable or USB (universal serial bus).

FIG. 8 is a block diagram of an electronic configuration of a videodecoding apparatus 800 according to an aspect.

Video decoding apparatus 800 uses adjacent block(s) to a video currentblock to predict the current block and decodes the video, and itincludes a decoder 810, inverse quantizer 820, inverse transformer 830,adder 840, and intra predictor 850.

Similar to video encoding apparatus 300 described with reference to FIG.3, video decoding apparatus 800 may be a personal computer or PC,notebook or laptop computer, personal digital assistant or PDA, portablemultimedia player or PMP, PlayStation Portable or PSP, or mobilecommunication terminal, smart phone or such devices, and represents avariety of apparatuses equipped with, for example, a communicationsystem such as a modem for carrying out communications between variousdevices or wired/wireless communication networks, a memory for storingvarious programs for encoding videos and related data, and amicroprocessor for executing the programs to effect operations andcontrols.

Decoder 810 decodes the bitstream and extracts a residual signal. Inother words, decoder 810 decodes the encoded video of the bitstream toextract the residual signal, which contains pixel information of thecurrent block in the video.

Inverse quantizer 820 inversely quantizes or performs de-quantizationwith respect to the extracted residual signal from the bitstream.Inverse transformer 830 inversely transforms the de-quantized residualsignal from inverse quantizer 820 into a time-domain domain.

Adder 840 adds predicted pixel values of respective current block pixelsfrom intra predictor 850 to the inversely transformed residual signalfrom inverse quantizer 820 to reconstruct the actual pixel value of thecurrent block.

To predict the current block, intra predictor 850 calculates thepredicted pixel values of the current block by weighting pixel values ofone or more adjacent pixels in one or more blocks which are among manypreviously decoded and reconstructed video blocks and neighboring thecurrent block.

The value for weighting may vary depending on the distances between therespective current block pixel(s) and the neighboring block adjacentpixel(s). In addition, intra predictor 850 may operate only with the DCmode prediction for the weighting to calculate the predicted pixelsvalues of the respective current block pixels.

Besides, intra predictor 850 of video decoding apparatus 800 may workthe same as or similar to intra predictor 310 of video encodingapparatus 300 in predicting the current block by using the neighboringblocks. Therefore, more detailed descriptions are omitted to avoidrepeated description.

FIG. 9 is a flow diagram of a video decoding method according to anaspect.

Video decoding apparatus 800 having received and stored the bitstreamfor the video through the wired/wireless communication network seeks toreproduce the video in accordance with a user selected or other programalgorithm in execution by predicting the video current block using itsneighboring block(s) and decoding the video and then reproducing thesame.

To this end, video decoding apparatus 800 decodes the bitstream toextract a residual signal which indicates information on the pixelvalues of the video current block in step S910. Upon extracting theresidual signal, video decoding apparatus 800 inversely quantizes theextracted residual signal in step S920, inversely transforms theinversely quantized residual signal into the time domain in step S930,predicts the current block by calculating the predicted pixel values ofthe respective current block pixels with a weight value applied to thepixel value(s) of the adjacent pixel(s) in the neighboring block(s) withrespect to the current block that the time-domain-intra-transformedresidual signal represents in step S940, and in step S950 adds thepredicted pixel values of the respective predicted current block pixelsof step S940 to the residual signals of the inversely transformedcurrent block of step S930 in order to reconstruct the original pixelvalue of the current block.

FIG. 10 is an exemplary diagram a process of predicting the currentblock by using a variable weighted value by pixel distances according toan aspect.

The intra prediction is typically performed using “multiple intraprediction modes” including a DC mode in which the averaged value ofpreviously encoded neighboring block pixels (possibly the left sideblock pixels and upper side block pixels in particular) is used topredict the pixel values of the entire current block pixels and in turnthe current block.

In FIG. 10, there are shown pixels used in the intra_(—)4×4 predictionof H.264, one of the video compression technical standard. The sixteensmall letters ‘a’ to ‘p’ represent the pixels in the current block to beencoded, and the sixteen capital letters A to M represent the previouslycompressed neighboring block pixels (i.e., adjacent pixels).

Applying the nine intra prediction modes for the typical intra_(—)4×4mode prediction described referring to FIG. 1 to performing the intraprediction with respect to the current block as shown in FIG. 10, ninedirections of predictions are made by using the pixel values of thepreviously compressed neighboring blocks A to M, and the optimumprediction mode is determined by using rate-distortion optimization orRDO among the nine intra prediction modes.

When applying the DC mode numbered 2 as shown in FIG. 1 to predictingthe pixel values of the current block pixels as shown in FIG. 10, theknown prediction methods arrange the sixteen pixels a through p to bepredicted as a single value. For example, at the first row and the firstcolumn pixel ‘a’ has a predicted pixel value calculated by equation 1 aswith the remaining pixels ‘b’ through ‘p’. Thus, the current blockpixels are predicted to be commonly valued regardless of theirpositions.

a=(A+B+C+D+I+J+K+L)/8  Equation 1

As described, because such a typical method for predicting pixel valuesof the current block using the DC mode does not differentially value therelative distances of the current block pixels to the adjacent pixels (Athrough L) but predicts as the common pixel value, it has beenimpossible to predict accurate pixel values by the pixel positionswithin the current block.

Actually, though the original pixels in the current block to be encodedmay have the common value, they may also have different pixel valuesthat the closer the current block pixels are to the adjacent pixels, thestronger the similarity gets to the adjacent pixels, while the fartherthe current block pixels are to the adjacent pixels, the weaker thesimilarity gets to the adjacent pixels. Specifically, the pixel valuesof the current block pixels are more probable to be similar to the pixelvalues of the adjacent pixels as these pixel-to-pixel distances getcloser. However, the known current block pixel value prediction methodusing the DC mode ignores such a positional relationship between thecurrent block pixels and the adjacent pixels resulting in the entirepixels being predicted as commonly assigned the averaged value of thepixels values of the adjacent pixels.

On the contrary, an aspect of the present disclosure counts thepositional relativity between the current block pixels and the adjacentpixels in predicting the pixel values of the current block pixels.

For example, when a prediction is performed on the pixels values of thepixels used the intra_(—)4×4 prediction, the pixel values are calculatedby applying a weight value to the sixteen a to p pixels' left sideblock's adjacent pixels (I, J, K, L) and their upper side blocks'adjacent pixels (A, B, C, D).

Here, the weighting value may be determined in inverse proportion tocalculations of the distances between the current block pixels to beencoded and the neighboring blocks' adjacent pixels. In other words, inpredicting the pixel values of the respective current block pixels byusing the pixel values of their neighboring block adjacent pixels (forexample, the pixel values of the left side blocks' adjacent pixels andupper side blocks' adjacent pixels), the present disclosure determinesthat a shorter distance between the current block pixels and theneighboring blocks' adjacent pixels indicates a stronger similaritybetween the current pixels and the adjacent pixels and heavily weightsthe pixel values of the neighboring blocks' adjacent pixels, whereas alonger distance between the current block pixels and the neighboringblocks' adjacent pixels is deemed representing a weaker similaritybetween the current pixels and the adjacent pixels and a smaller weightvalue is applied to the pixel values of the neighboring blocks' adjacentpixels.

In an aspect of the disclosure as described, the pixel values of therespective current block pixels are predicted by performing weightedaveraging of pixels values of the one or more adjacent pixels in theneighboring blocks to the current block depending on the distancesbetween the respective current block pixel(s) and the respectiveadjacent pixel(s). Equation 2 is to apply such a weighted averagingaccording to the pixel distance to predict the pixel values.

x=(f1×P1+f2×P2+ . . . +fn−1×Pn−1+fn×Pn)/N  Equation 2

Here, x represents the respective pixels in the current block (pixels ato p in FIG. 10), P1 through Pn are the neighboring blocks' adjacentpixels respectively (pixels A to L in FIG. 10), and f1, f2, . . . fn−1,fn are respectively the weight values depending on the distances betweenthe respective current block pixels x and the neighboring blocks'adjacent pixels P1 through Pn. In addition, N equals to f1+f2+ . . .+fn−1+fn.

Predicting the respective current block pixels ‘a’ to ‘p’ shown in FIG.10 by using Equation 2 may be expressed by Equation 3. However, toeasily describe about predicting the pixel values of the respectivepixels, the neighboring blocks are restricted to include the currentblock's left side blocks and upper side blocks, the adjacent pixels inthe neighboring blocks are also restricted to the adjacent pixels thatbelong to the corresponding row and column as those of the current blockand such adjacent pixels are used to predict the respective currentblock pixels. Though, the present disclosure is not restricted to such alimitation but may use partial or entire adjacent pixels in the currentblock's neighboring blocks to predict the current block.

a=(A+I)/2

b=(2B+I)/3

c=(3C+I)/4

d=(4D+I)/5

e=(A+2J)/3

f=(2B+2J)/4

g=(3C+2J)/5

h=(4D+2J)/6

i=(A+3K)/4

j=(2B+3K)/5

k=(3C+3K)/6

1=(4D+3K)/7

m=(A+4L)/5

n=(2B+4L)/6

o=(3C+4L)/7

p=(4D+4L)/8  Equation 3

Here, reviewing the pixel value of pixel ‘a’, it can be determined bythe upper side block's adjacent pixel A and the left side block'sadjacent pixel I, and pixel ‘a’ is equally located to the pixels A and Iwith a space of a single pixel (basic distance). Therefore, pixel ‘a’ inthe basic distance is calculated by applying a basic weight value ‘1’ tothe pixels A and I, and assuming the entire pixels are distanced oneanother by ‘1’, ‘a’ equals to (1×A+1×I)/(1+1)=(A+I)/2.

In addition, reviewing the pixel value of pixel ‘g’, it can bedetermined by the upper side block's adjacent pixel C and the left sideblock's adjacent pixel J, and pixel ‘g’ is distanced by two pixels(basic distance×2) from pixel C and three pixels (basic distance×3) frompixel J. Therefore, the weight value for calculating the pixel value ofpixel ‘g’ is assigned ‘2’ for pixel C and ‘3’ for pixel J, and assumingthe entire pixels are distanced one another by ‘1’, ‘g’ equals to(3×C+2×J)/(3+2)=(3C+2J)/5.

As described, in performing the DC mode prediction by using the pixelvalues of the neighboring block's adjacent pixels with the weight valueconsidered according to the distances between the current block pixelsand the neighboring blocks' adjacent pixels, no more the predicted pixelvalues of the current block are determined en bloc as has been typicalbut rather they can be predicted into different predicted pixel valuesby the positions of the respective current block pixels.

In the example aspect described with reference to FIG. 10, therespective single pixels from the current block's left side block andupper side block are used to calculate the predicted pixel value of thecurrent block. However, the present disclosure is not necessarilyrestricted to this example but may use a part or the entirety of thesixteen pixels a to p in the current block's left side block and upperside block to obtain the predicted value of a single pixel in thecurrent block, and additionally use current block's other partial orentire surrounding blocks' pixel value(s) partially or entirely toobtain the predicted value of the single pixel in the current block.

This prediction of the current block by using the pixel values of theadjacent pixels with the variable weight value incorporated depending onthe distances between the current block's pixels and the neighboringblocks' adjacent pixels is not only performed in video encodingapparatus 300 but equally performed in video decoding apparatus 800 byintra predictors 310 and 850.

As described, when video encoding apparatus 300 and video decodingapparatus 800 perform the DC mode predictions and upon determining thecurrent block went through the intra prediction in the DC mode, eitherthe intra_(—)4×4 prediction or the intra_(—)16×16 prediction counts thedistance-based weight value in predicting the pixel value of the currentblock to obtain the optimal predicted pixel value though finelyapproximating the predicted current block to the original current block,and thereby reducing the differential value between the original currentblock and the predicted one which keeps up the intra predictionperformance while improving the video compression efficiency andreducing the amount of data to be transmitted.

Although the above description is presented with video encodingapparatus 300 and video decoding apparatus 800 implemented asindependent devices, they may be implemented in a single unit. Thecomponents of video encoding apparatus 300 and video decoding apparatus800 of encoder 350, decoder 810, quantizer 340, inverse quantizer 820,transformer 330, inverse transformer 830, subtractor 320, adder 840, andintra predictors 310 and 850 may be independent hardware componentsimplemented respectively to include memories for storing programs andmicroprocessors for executing the programs to realize their functions,although they may be implemented as program modules for carrying out therespective functions within the hardware of video encoding apparatus 300and video decoding apparatus 800.

In addition, if video encoding apparatus 300 and video decodingapparatus 800 are implemented in a single unit, the counter functioningcomponent pairs of encoder 350 and decoder 810, quantizer 340 andinverse quantizer 820, transformer 330 and inverse transformer 830,subtractor 320 and adder 840, and intra predictors 310 and 850 may beimplemented in singular program modules, respectively.

As described above, various embodiments of the present disclosure isable to more accurately predict the current block to be encoded, tothereby close the gap between the original pixel and the predicted pixeltoward a heightened coding efficiency and improved video compressionefficiency.

Although exemplary aspects of the disclosure have been described forillustrative purposes, those skilled in the art will appreciate thatvarious modifications, additions and substitutions are possible, withoutdeparting from the spirit and scope of the claimed invention. Specificterms used in this disclosure and drawings are used for illustrativepurposes and not to be considered as limitations of the presentdisclosure. Therefore, the aspects disclosed in the present disclosurehave been described not for limiting the technical idea of thedisclosure, but for explaining the disclosure. Accordingly, the scope ofthe claimed invention should be interpreted by the appended claims,which by themselves and their equivalents are the claim scope of thedisclosure.

What is claimed is:
 1. A video decoding apparatus using an intraprediction, the apparatus comprising: a decoder configured to decode abitstream to thereby extract residual signals; an inverse quantizerconfigured to inversely quantize the residual signals; an inversetransformer configured to inversely transform the inversely quantizedresidual signals; an intra predictor configured to predict a currentblock from a plurality of neighboring blocks of the current block; andan adder configured to add the inversely transformed residual signals tothe predicted pixels in the predicted block, wherein the intra predictorcomprises: a weighted pixel calculator configured to calculate aplurality of weighted pixel values of pixels selected in the neighboringblocks by applying weights to the pixels selected in the neighboringblocks, wherein the weights are decided variably based on a position ofa current pixel to be predicted in the current block; and a pixelpredictor configured to derive a predicted pixel value of the currentpixel using the weighted pixel values, and wherein the pixels selectedin the neighboring blocks comprise: a first pixel which is included inan upper neighboring block and located at the same column with thecurrent pixel; and a second pixel which is included in a leftneighboring block and located at the same row with the current pixel. 2.The apparatus of claim 1, wherein the weighted pixel values comprise: afirst weighted pixel value calculated by applying a first weight of theweights to the first pixel in the upper neighboring block, and a secondweighted pixel value calculated by applying a second weight of theweights to the second pixel in the left neighboring block.
 3. Theapparatus of claim 2, wherein the first weight is decided by thedistance between the current pixel and the first pixel in the upperneighboring block, and the second weight is decided by the distancebetween the current pixel and the second pixel in the left neighboringblock.
 4. The apparatus of claim 1, wherein the weights are decided bythe distance between the current pixel and each of the pixels selectedin the neighboring blocks.
 5. The apparatus of claim 1, wherein agreater weight is applied to a pixel having a shorter distance from thecurrent pixel among the pixels selected in the neighboring blocks. 6.The apparatus of claim 1, wherein the predicted pixel value of thecurrent pixel is derived by dividing a sum of the weighted pixel valuesby a sum of the weights.
 7. The apparatus of claim 1, wherein theweighted pixel values further comprise one or more third weighted pixelvalues calculated by applying third weights of the weights to one ormore third pixels in the neighboring blocks.
 8. The apparatus of claim1, wherein the weighted pixel values further comprise: a third weightedpixel value calculated by applying a third weight of the weights to athird pixel located at an upper outside of the current block, and afourth weighted pixel value calculated by applying a fourth weight ofthe weights to a fourth pixel located at an left outside of the currentblock.